Electric Motor Calculator

You can read this while the Applet loads

As a rule of thumb, you will want 30 to 40 watts per pound of OUTPUT power for good climbing performance. Depending upon drag, a model will fly level with about 10 to 15 watts per pound. You will need enough pitch speed to reach the design flying speed at the power levels you choose.

The program will show that higher voltage produces better efficiency and it will be much easier to reach the desired power output with more voltage to the motor. I wouldn't stress input power as something to look at ( a common rule of thumb being 50 watts of input power per pound ). The program shows it is pretty easy to find combinations that produce plenty of input power, but not so much output power. For more power, it is better to increase the gear ratio, prop size and add more voltage, than to increase the current. On the other hand, lower voltages will result in less heating of the battery elimination circuit (BEC) of your ESC. Fewer cells are also lighter and cheaper. Many ESC's are derated at higher voltages ( meaning can drive fewer servos ).

The program ignores friction in the motor bearings. The calculations do not consider that a larger propeller turning slower will work better that a smaller propeller turning fast. The output text area will stop working if it gets too full. You can edit this area. Keep the combinations that interest you, select and delete the others.